On folic acid, alcohol and cancer

There is a growing body of epidemiological and experimental evidence suggesting a causal role for inadequate dietary consumption of folic acid in the carcinogenesis of breast and colorectal cancers.

Three previous studies have examined the role of folate intake and ovarian cancer. A study that appeared in the March 3 issue of the Journal of the National Cancer Institute examined how alcohol modified the risk relation between dietary folic acid consumption and ovarian cancer.

The study was based on information from the Swedish Mammography Cohort, a large, prospective, population-based study involving 61,000 women who entered the study between 1987 and 1990. At the time of entry, none had ovarian cancer. In 1990 they responded to a self-administered food frequency questionnaire that included 67 food items, including folic acid and alcohol. The mean follow-up for this group was 13.5 years.

The study found a strong inverse relation between ovarian cancer and folic acid intake among women who consumed more than 20 grams of alcohol per week. Those who were in the highest quartile of folic acid (found in fruits and vegetables) intake and consumed more than two drinks per week experienced a 74 percent reduction of risk of developing ovarian cancer. Those who drank more than four drinks per week and were in the highest quartile of folic acid intake had an 85 percent risk reduction for being diagnosed with ovarian cancer. Those who consumed fewer than two drinks per week did not benefit from being in the highest quartile of folic acid intake.

According to the study analysis, the risk of ovarian cancer for women who drink more than two drinks per week can be reduced by 50 percent if they increase their folic acid consumption by a mere 50 micrograms, which amounts to an extra orange per day.

This study did not show any association of either folic acid or alcohol with ovarian cancer when each was analyzed individually. The strong beneficial effect was found only when both were analyzed together.

In critical analysis, a strong outcome when two variables are combined which individually had no effect by themselves, would be viewed suspiciously. This rule of thumb, however, does not rule out a combined effect of two seemingly neutral variables. So, based upon this study and common sense, it would be easy to recommend liberal intake of fruits and vegetables for women who consume more than two alcoholic drinks per week.

What is difficult to recommend is the optimal amount of alcohol consumption. There is much in the literature noting that alcohol has a protective effect on cardiovascular mortality but a deleterious association to various cancers. While alcohol's association with many cancers is common knowledge, a scientific basis and rationale has been elucidated for breast, pancreas and colorectal cancers.

Alcohol induces the estrogen receptor that creates a conducive environment for the development of breast cancer; it causes chronic inflammation in the pancreas, which has been shown to increase the risk of cancer; and it alters the iron homeostasis in such a manner that its metabolites become pro-oxidant (as opposed to antioxidant), which makes the colorectal lining more susceptible to cancer.

Based on statistics, a woman is much more likely to die from cardiovascular disease than ovarian cancer. In view of the protective effect of alcohol on cardiovascular mortality, it is not prudent to restrict a woman's alcohol consumption to two or fewer drinks per week. Instead, it would be both easy and simple to recommend a liberal intake of fruits and vegetables, daily moderate physical activity, a calorie-restricted diet, avoidance of tobacco and moderate alcohol consumption.